In order to ensure quality and yield in manufacturing processes for magnetic disk drives (HDDs), it is essential to screen out nonconforming magnetic heads from a finished lot. To that end, HGAs (head gimbal assemblies), in which the magnetic heads are built, are typically subjected to a DET (dynamic electric test). The DET measures such parameters as output, overwrite, resolution, and a track width of the magnetic head, thereby selecting HDDs that are fully operational. To achieve good measurement accuracy in these parameters, a known DET tester includes a high accuracy spin stand, a high accuracy position control system, and a high performance electronic circuit system. The spin stand rotates a disk. The position control system controls the position of the head during read and write operations with high accuracy. The electronic circuit system accomplishes read and write operations with a level of performance equivalent to that of the HDD product. Such a high accuracy spin stand, high accuracy position control system, and high performance electronic circuit system are, however, costly, resulting in a single tester unit costing as much as tens of millions of yen. Preparing testers in large numbers thus requires a tremendous amount of investment.
To reduce the cost of such a high-priced DET tester, a method is being examined whereby components of a product HDD are used as components making up the tester. For example, “The Technical Report of the Institute of Electronics Information and Communication Engineers of Japan”, Denshi Joho Tsushin Gakkai Shingaku Giho, Vol. 103, No. 495, MR2003-39-44, pages 1-5 (“Non-patent Document 1”) discloses a spin stand which is all but an actual drive designed to facilitate replacement of the magnetic head and the magnetic disk, by carrying over functions of an actual spindle motor and an actual VCM (voice coil motor). Non-patent Document 1 further describes that servo information written in the magnetic disk is demodulated with a PRML (partial response maximum likelihood) chip, thereby allowing the VCM to perform real-time following. Japanese Laid-Open Patent No. 2001-110126 (“Patent Document 1”) discloses an arrangement, in which a VCM actuator is used as the magnetic disk evaluation apparatus and which includes a spin stand having a mechanism equivalent to that of an actual HDD. Japanese Patent Publication No. 5-120646 (“Patent Document 2”) discloses a magnetic head inspection apparatus including a mechanism that fixes an HGA spacer to a mount with a leading end of a spring.
As described above, an attempt is made to realize a low-priced DET tester by using components of the product HDD even in the known art. In the art as disclosed in Non-patent Document 1, however, to achieve track following, a servo track writer having a high accuracy rotary positioner and an air spindle with a small NRRO (non-repeatable run out) is used to write a servo pattern in a disk for evaluation. This results overall in a large-sized, high-priced evaluation system. Non-patent Document 1 also mentions that the art enables evaluation of heads and disks; however, the HGA is mounted to the actuator arm manually using screws. Patent Document 1 is concerned with a magnetic disk evaluation apparatus, in which it is necessary to write a servo signal in an entire surface of the magnetic disk in advance before position control of the evaluation HGA can be performed. In this apparatus as disclosed in Patent Document 1, the magnetic disk is replaced each time a test is made, but the HGA is generally used until it breaks. Replacement frequency of the HGA is thus extremely low. Accordingly, the HGA is replaced manually by using screws for fixing the HGA on the arm of the VCM actuator. Disadvantageously, however, the magnetic head evaluation apparatus requires that HGA be replaced each time a test is made. From standpoints of productivity and electrical and mechanical damage caused by manual labor, it is not desirable to remove and reinstall the HGA using the screws for each test.
To solve a problem that a magnetic head evaluation apparatus, which incorporates a high accuracy spin stand and a high accuracy head position control system, is extremely expensive.